Influence of Asellus aquaticus on Escherichia coli, Klebsiella pneumoniae, Campylobacter jejuni and naturally occurring heterotrophic bacteria in drinking water

Zooplankton act as cruise ships promoting the survival and pathogenicity of pathogenic bacteria

Bacteria in general interact with zooplankton in aquatic ecosystems. These zooplankton-bacterial interactions help to shape the bacterial community by regulating bacterial abundances. Such interactions are even more significant and crucially in need of investigation in the case of pathogenic bacteria, which cause severe diseases in humans and animals. Among the many associations between a host metazoan and pathogenic bacteria, zooplankton provide nutrition and protection from stressful conditions, promote the horizontal transfer of virulence genes, and act as a mode of pathogen transport. These interactions allow the pathogen to survive and proliferate in aquatic environments and to endure water treatment processes, thereby creating a potential risk to human health. This review highlights current knowledge on the contributions of zooplankton to the survival and pathogenicity of pathogenic bacteria. We also discuss the need to consider these interactions as a risk factor in water treatment processes.

Ecology and etiology of bacterial top rot in maize caused by Klebsiella pneumoniae KpC4

Klebsiella pneumoniae is an important opportunistic pathogen in humans and animals. Recently, K. pneumoniae KpC4 was identified as a causative agent of bacterial top rot in maize, which has been observed in many areas of Yunnan province, China. KpC4 is potentially dangerous to humans and livestock due to its cross-kingdom infection ability. Our study revealed the disease cycle of maize bacterial top rot caused by KpC4 and the ecological adaptability and host range of KpC4. We found same pathogenicity in maize between KpC4, the environmental strains E1, E4 (K1 serotype), E5, and the clinical strain K. pneumoniae 138 (Kp138). Alternative hosts of K. pneumoniae include not only humans and animals but also a variety of plants (such as maize, banana and sorghum). One of the survival strategies of K. pneumoniae is ecological adaptability, which is an essential factor for KpC4 to be able to cause bacterial top rot in maize. K. pneumoniae, for example, could survive in large numbers (2.34 ± 0.22 × 10³ cfu/g) not only in the maize leaves (2.34 ± 0.22 × 10³ cfu/g) under natural light, but persist in dried maize plant debris (1.51 × 10⁴ cfu/g) for at least 6 months. K. pneumoniae strains from different sources can generally induce infection in susceptible hosts. Thus, this study revealed the ecological basis of KpC4 cross-kingdom infections, laying the foundation for the study of the mechanisms underlying cross-kingdom infections involving this type of human/animal opportunistic pathogen.

Asellus aquaticus as a potential carrier of Escherichia coli and other coliform bacteria into drinking water distribution systems

Individuals of the water louse, Asellus aquaticus, enter drinking water distribution systems in temperate parts of the world, where they establish breeding populations. We analysed populations of surface water A. aquaticus from two ponds for associated faecal indicator bacteria and assessed the risk of A. aquaticus transporting bacteria into distribution systems. Concentrations of up to two E. coli and five total coliforms·mL-1 were measured in the water and 200 E. coli and >240 total coliforms·mL-1 in the sediments of the investigated ponds. Concentrations of A. aquaticus associated bacteria never exceeded three E. coli and six total coliforms·A. aquaticus-1. During exposure to high concentrations of coliforms, concentrations reached 350 coliforms·A. aquaticus-1. A. aquaticus associated E. coli were only detected as long as E. coli were present in the water and sediment. The calculated probability of exceeding drinking water guideline values in non-disinfected systems by intrusion of A. aquaticus was low. Only in scenarios with narrow pipes and low flows, did total coliforms exceed guideline values, implying that the probability of detection by routine monitoring is also low. The study expands the knowledge base for evaluating incidents with presence of coliform indicators in drinking water by showing that intruding A. aquaticus were not important carriers of E. coli or other coliform bacteria even when emerging from faecally contaminated waters.